This invention relates to a tone signal generation device capable of generating a tone signal having a tone color controlled in accordance with key touch or other tone color control factors and, more particularly, to a tone signal generation device generating a tone signal by properly weighting waveshape signals of plural channels having different characteristics and combining these weighted waveshape signals. The invention relates also to a tone signal generation device capable of changing functions used for weighting in accordance with a selected tone color.
In order to generate a tone waveshape signal of a high quality, it has recently been practiced to store either a full waveshape from the start of sounding of a tone to the end thereof or a full waveshape of an attack portion and a part of the subsequent waveshape and read out the full waveshape once when the full waveshape has been stored or read out the waveshape of the attack portion once and then the part of the subsequent waveshape repeatedly (U.S. Pat. No. 4,383,462). This system according to which a continuous waveshape of multiple periods is stored in a waveshape memory requires a memory of an extremely large memory capacity while it can produce a tone waveshape signal of a high quality and, for this reason, it is unsuitable for realizing various tone color changes according to the key touch, tone pitch or other tone color control factors. For effecting a key scaling control in which the tone color is changed in accordance with the tone pitch or tone range of a tone to be produced, or a touch response control in which the tone color is changed in accordance with a state of operation (speed or strength of operation) of a playing key, or an operation knob control in which the tone color is changed in accordance with a state of operation of various operation knobs (e.g. a soft pedal and a brilliance operation knob), the simplest way would be to provide a plurality of memories, one for each of these different controls, and access a selected one of these memories. This, however, would necessitate a complex construction requiring a large memory capacity and therefore would be unrealistic. As an alternative, it has been conceived, as disclosed in Japanese Patent Preliminary Publication No. 60-55398, to prepare in a waveshape memory two types of continuous waveshapes, e.g., a continuous waveshape corresponding to the strongest touch and a continuous waveshape corresponding to the weakest touch in the case of the touch response control, read out the two waveshapes simultaneously and interpolate the two waveshapes in accrodance with a tone color change parameter (i.e., touch strength) to obtain a waveshape corresponding to the tone color change parameter (touch strength). Even in this case, however, a full waveshape from the start of sounding of the tone to the end thereof must be stored so that the problem of requiring a large memory capacity remains unsolved. Further, in this proposed system, it is desirable to bring waveshapes to be stored in phase with each other in storing the respective waveshapes so as to perform the interpolation operation smoothly. Since, however, copies of waveshapes of actually performed tones are generally used as two waveshapes to be stored in a waveshape memory, an operation for bringing the waveshapes in phase is not an easy task.
In natural musical instruments generally, tone color change characteristics according to the touch strength or tone color change characteristics according to the tone pitch or tone range are not uniform for all types of natural musical instruments but are different depending upon the kind of natural musical instrument. Such tone color change characteristics exhibiting proper characteristics of a particular musical instrument characterizes, together with the constant tone color of the musical instrument, a tone color proper to the musical instrument.
In the prior art devices including the above described patent and patent application, however, no consideration was given to such tone color change characteristics proper to each natural musical instrument in determining function characteristics for the interpolation operation. Accordingly, a common weighting function for interpolation had to be employed irrespective of the kind of tone color selected in an electronic musical instrument (corresponding typically to natural musical instruments such as piano and guitar). Consequently, the prior art devices failed to strictly simulate tone color change characteristics proper to respective natural musical instruments.